Color displays are an important component in any imaging workflow and often require calibration to ensure true color is presented on the displays. In certain fields, particularly the area of graphic design, it is essential to ensure that a display presents true color to ensure the color of the image. Currently, calibration can be carried out using either an optical measurement device, such as a luminance meter, or by visual calibration.
Display calibration is accomplished by ensuring that the gamma used for a display is correct. The gamma level controls the brightness of an image, thus images without the proper gamma can appear either too light or too dark. When the correct gamma is used, the images presented on a display are in true color, and thus accurately represent the color of the image.
As stated above, one way to determine the gamma of a display is by using an optical measurement device, such as a luminance meter. Colorimetric models exist which can accurately predict the tristimulus values of a given set of input RGB values for a specific monitor. However, these models require the measurement of a test target by an optical measurement device in order to fit the parameters of the model. Many display users do not own such measurement equipment, because the equipment is typically expensive. Furthermore, optical measurement devices may be difficult to operate and handle, thus reducing their desirability and usability.
Another way to determine the gamma of a display is by using a visual calibration procedure in which a human observer substitutes for a measurement device. There are currently a number of visual calibration procedures for determining gamma. For example, one procedure requires the observer to match stimuli, such as matching a uniform gray to a black and white checkerboard. The user adjusts the gray level of a square to match the lightness of a square consisting of a black and white checkerboard. The results of this adjustment can be used to estimate the gamma. The observer then adjusts the lightness of a dark square until it is just visible relative to the device black. The results of this adjustment can be used to estimate the offset term. This approach requires careful adjustment of both test patches and requires two steps in order to complete. There are also visual calibrations that make use of a printed reference sample to guide the user during calibration.
Accordingly, a need exists for a method for estimating the gamma level of a display without requiring the use of a physical reference standard, multiple screens, or the matching of stimuli. Furthermore, a need exists for a method that accomplishes the above need and is simple to use. A need also exists for a method that accomplishes the above needs and does not require the use of an optical measurement device.